title: A prospective evaluation of two defibrillation safety margin techniques in patients with low defibrillation energy requirements.
abstract: BACKGROUND
  In patients undergoing defibrillator implantation, an appropriate defibrillation safety margin has been considered to be either 10 J or an energy equal to the defibrillation energy requirement. However, a previous clinical report suggested that a larger safety margin may be required in patients with a low defibrillation energy requirement. Therefore, the purpose of this prospective study was to compare the defibrillation efficacy of the two safety margin techniques in patients with a low defibrillation energy requirement.
  
  
  RESULTS
  Sixty patients who underwent implantation of a defibrillator and who had a low defibrillation energy requirement (< or = 6 J) underwent six separate inductions of ventricular fibrillation, at least 5 minutes apart. For each of the first three inductions of ventricular fibrillation, the first two shocks were equal to either the defibrillation energy requirement plus 10 J (14.6+/-1.0 J), or to twice the defibrillation energy requirement (9.9+/-2.3 J). The alternate technique was used for the subsequent three inductions of ventricular fibrillation. For each induction of ventricular fibrillation, the first shock success rate was 99.5%+/-4.3% for shocks using the defibrillation energy requirement plus 10 J, compared to 95.0%+/-17.2% for shocks at twice the defibrillation energy requirement (P = 0.02). The charge time (P < 0.0001) and the total duration of ventricular fibrillation (P < 0.0001) were each approximately 1 second longer with the defibrillation energy requirement plus 10 J technique.
  
  
  CONCLUSIONS
  This study is the first to compare prospectively the defibrillation efficacy of two defibrillation safety margins. In patients with a defibrillation energy requirement < or = 6 J, a higher rate of successful defibrillation is achieved with a safety margin of 10 J than with a safety margin equal to the defibrillation energy requirement.
authors.affiliation: University of Michigan Medical Center, Ann Arbor 48109-0022, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Strickberger
authors.forename: K C
authors.initials: KC
authors.lastname: Man
authors.forename: J
authors.initials: J
authors.lastname: Souza
authors.forename: A
authors.initials: A
authors.lastname: Zivin
authors.forename: R
authors.initials: R
authors.lastname: Weiss
authors.forename: B P
authors.initials: BP
authors.lastname: Knight
authors.forename: R
authors.initials: R
authors.lastname: Goyal
authors.forename: E G
authors.initials: EG
authors.lastname: Daoud
authors.forename: F
authors.initials: F
authors.lastname: Morady
mesh_terms: D000368:Aged; D017147:Defibrillators, Implantable / Q000009:adverse effects / Q000592:standards*; D004554:Electric Countershock / Q000009:adverse effects / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies